Commonly, substance delivery devices inserted into a living animal for dispensing substances to the animal also employ retention apparatus. Accordingly, a range of retention apparata exist for retaining the substance delivery device within a passage or body cavity of an animal.
Some systems commonly used for retaining delivery devices capable of being inserted into a body cavity of an animal, incorporate a compressible helica coil, such as in U.S. Pat. Nos. 228,382 and 190,350. The compressible coil is frequently capable of returning to the required shape after the device has been inserted into the animal's body cavity.
However, such coils rely on the overall bulk of the coil to retain the coil within the body cavity of an animal. Accordingly, the bulkiness of the coil may impede the flow of body secretions which may not be desirable. An unimpeded flow of body secretions is necessary for the normal biological functioning of the animal. Such body secretions include mucus, where such a device is used intravaginally.
In addition, the coil is typically capable of expanding and pressing against a considerable area of the wall of a body cavity of an animal, to the extent that it may be too bulky to pass back through passages leading into or out of the body cavity. Accordingly, when the functional utility of the device has been exhausted, removal of the device may be difficult.
Other systems commonly employed for retaining devices within the body cavity of an animal have incorporated a number of lobes, similar to those of U.S. Pat. No. 193,976 and U.S. Pat. No. 200,564. These lobes are often flexible enough to fold over onto each other for insertion into a body cavity of an animal and then spring open after the device is inside the animal. Frequently, the lobes perform a dual purpose of retaining the device within an animal's body cavity and of releasing an active ingredient, often impregnated into the lobe or in the coating around the lobe, into the animal's body cavity. Accordingly, the lobes may have a substantial, even rippled, surface area to ensure that sufficient active ingredient is available to perform the required function. In addition, the lobes are often specifically designed to provide a large surface area to enable the animal's body fluids to act on those surfaces to leach out active ingredients contained within the lobes.
However, the surface area of these devices is again capable of impeding the flow of body secretions. In addition, the natural elasticity of the lobes enables the lobes to be folded over onto each other to enable the device to be inserted into and removed from the animal's body cavity. However, an operator may be required to manually hold the lobes in the folded orientation, during insertion of the device into the animal's body cavity.
Further systems incorporate hinged legs or branched members, as in U.S. Pat. Nos. 215,635 and 230,023, which may extend from one or both ends of the body of a device inserted into the body cavity of an animal. Again, these legs or members, as well as the body of the device, are typically impregnated with active ingredients required to be dispensed into the animal. Accordingly, it is desirable that the legs or members add to the overall surface area of the device to enable the active ingredients to be more efficiently leached from the device and into the animal. Again, the common problem associated with such devices and retention systems for these devices, is that initially the increased surface area may impede the flow of the animal's internal body secretions. Particularly, the flow of mucus in the vagina of the animal.
However, with time, erosion of the polymer layers which contain the active ingredients, effectively reduces the surface area, overall size, and overall weight of the device. A problem is therefore that as the device gets smaller and lighter it does not have the same retentive ability.
In addition, such systems typically require an applicator, such as those described in U.S. Pat. Nos. 215,483 and 207,341. These applicators hold the legs or members into a required position to enable the device and the retention apparatus to be inserted into the animal's body cavity.
Often the applicators are complex or bulky structures, and are separate from the devices which they are capable of inserting. Inclusion of an applicator with the device may increase the costs of manufacture, and require insertion of the device into the applicator thereby extending the time associated with inserting devices into the animals.
Yet other systems may incorporate a number of distensible ribs, such as in U.S. Pat. No. 173,926. The ribs are capable of being distended into a possible retaining position by the action of a plunger system. When the plunger system is released the distensible ribs return to the undistended position for withdrawal. However, these devices are typically used for single applications of pharmaceutical formulations into the body cavity of an animal and are not intended to, nor are suitable for, retaining device over longer periods. The bulkiness of the plunger system, if left attached to the device could be a source of discomfort to the animal; the distensible ribs are typically unsuited to retaining a device in a larger body cavity; and the surface area of the ribs would impede the body's flow of secretions.
Yet other retention devices may be of sufficient dimensions to be retained in the body cavity of an animal by relying on muscle tension around the retention device. Such devices are typically used as intra-vaginal contraceptive devices for animals, such as in U.S. Pat. No. 173,808. However, the dimensions of the retention device may prevent penile insertion during attempted intermission by the male animal, and for impede flows of body secretions, particularly vaginal mucus.
Accordingly, it would be desirable if the retention apparatus of a substance delivery device enabled the delivery device to be easily inserted and removed, yet was reliably retained for required periods, and did not impede flow of body secretions or adversely affect normal functioning by its mere physical presence.
Similarly, a range of delivery apparata for delivering substances are well known, and have broad application.
Many incorporate pumps and are used to dispense common substances such as petrol and air. Some delivery apparata are used inside a living animal to dispense useful substances such as chemicals or drugs.
For example, there are a number of delivery apparata known that introduce substances such as hormones intravaginally to cows. The purpose of such apparata is to promote with some accuracy the onset of oestrus. This enables the farmer to artificially inseminate the cows at a time when they are most fertile.
For example, New Zealand Patent No. 228382 discloses such a delivery apparatus. The device disclosed consists of a helical coil made up of a number of segments. These segments contain useful substances which are either impregnated into or coated onto.
The substance to be administered to the animal is gradually released from the segments of the apparatus over a period of time by the action of body fluids. Accordingly, such apparatus relies on the natural processes of diffusion, dissolution, or osmosis to dispense the substance.
Various other delivery apparata as described in New Zealand Patent Nos. 207341, 200564 and 215635 all release drugs into the body cavity passively, as consequence of the action of body fluids.
However, when controlling oestrus in animals for example, different hormones or concentrations need to be released into the animal's body at different times. To effect this, previous delivery apparata have had a number of layers, perhaps with different thicknesses, containing both passive and active substances. These enter the body by the diffusion, dissolution or osmosis, all these processes being dependent upon the body fluids surrounding the substance delivery device or delivery apparata within the device.
For example, it may be desirable to introduce into the body for a period of ten days a certain hormone, then no hormone for another ten days and then introduce another hormone for another period of time. The delivery device could have layers of thicknesses proportional to the time it is estimated that these layers will take to dissolve into the body system.
Unfortunately, there are problems associated with these devices incorporating such delivery apparata. All of these devices are passive devices dependent upon the body fluids surrounding them for the introduction of the active substances into the body.
However, the rate of introduction of these substances is dependent upon a number of factors such as the temperature, mucus concentration, salt concentration, kinetic action and so forth of the body fluids. These factors are variable from animal to animal which leads to variable timing and concentration of the substances being introduced into the body.
Further, with the substances being exposed to the body's environment, it is possible for the layers to be chipped and a completely inappropriate substance introduced into the body at the wrong time. Hence, such systems tend to restrict themselves to delivery of a single active material or if more than one, the second material is introduced at the start.
In addition, once these delivery devices are inserted into an animal, the delivery of substance into the animal cannot be controlled as it is totally dependent upon the environment that it is in.
The ability to control the amount and timing of dispensation of a substance with any degree of accuracy is difficult, as there is a dependence upon the external environment to provide the conditions necessary for dispensation to occur, with the conditions determining the volume and rate of dispensation. Accordingly, delivery apparatus reliant on osmosis, diffusion, and dissolution all suffer from inaccuracy in dispensing and inherently have little timing precision.
Alternately, conventional pumps are often large and complicated. They contain moving parts, complex valve systems, are usually difficult to operate with any degree of accuracy, and are often not suitable for insertion into an animal's body. Further, conventional pumps often require regular maintenance.
It would therefore be desirable if there could be provided a delivery device which was small and simple, contained no complex parts, was maintenance free, and which could be used in animal's bodies or other such environments.
It would also be desirable if there could be provided a device which included delivery apparatus capable of being accurately operated to deliver substances into an animal in precise concentrations and with precise timing, and where such a apparatus could operate independently of the environment, or the apparatus could release substances into the environment only when the environment was ideal.
In addition, it would be desirable if there could be effected some control over the delivery apparatus after the device is placed in the animal, and/or if there was some way of determining what was happening within the animal with respect to the operation of the device and associated delivery apparatus.
It is an object of the present invention to address the above problems or at least to provide the public with a useful choice.
Further objects and advantages of the present invention will now be discussed by way of example only.